small cold room evaporator design

[sunilbhat]

Can Anybody guide me,what are thumb rules for selection of cooling coils and fan air throw requirement for fruit preservation room where +5 celcius temp to be maintained and max possible RH ( 90%) to be maintained.

Room Size varies from 1000 cubic feet to 5000 cubic feet of puf panels.

Thanks Sunil Bhat

[750 Valve]

Big coils with low TD's is what you want. The lower the TD the higher the room RH. If you really want to get it spot on use a psych chart and plot you desired conditions.

[Samarjit Sen]

Hello Sunil Bhat,

There are no thumb rules for evaporator selection. First you have to work out the heat load taking the product, product weight, incoming temperature, ambient temperature into consideration. Also the Rh has to be taken. On the basis of the heat load you select the Evaporator. Yes the Evaporator face area has to be large, which means high air discharge and keep the Td low. You can get the Evaporator sizing from any catalogs or design selection of Evaporator manufacturers.

In case you need any further help. please do let me know and I shall try to assist you. Please remember that you are doing Fruit Storage or Precooling and as such you have to be precise in your selection of all the equipments and controls.

[sunilbhat]

Hello Sunil Bhat,

There are no thumb rules for evaporator selection. First you have to work out the heat load taking the product, product weight, incoming temperature, ambient temperature into consideration. Also the Rh has to be taken. On the basis of the heat load you select the Evaporator. Yes the Evaporator face area has to be large, which means high air discharge and keep the Td low. You can get the Evaporator sizing from any catalogs or design selection of Evaporator manufacturers.

In case you need any further help. please do let me know and I shall try to assist you. Please remember that you are doing Fruit Storage or Precooling and as such you have to be precise in your selection of all the equipments and controls.

Dear Sir,

Thank you very much for your valuable guidelines.

I have arrived at heat load considering
1 wall transimission load
2 Air change ( Infilteration) load
3 product load ( sensible,latent,respiration)
4 electrical and occupancy load.

But for given load how to arrive to surface area ( Primary and secondary) and air flow desired which will keep RH 90% and desired temp between +5 to +10 degree celcius.

I will be grateful for your help

Thanks Sunil Bhat

[lana]

Dear Sir,

Thank you very much for your valuable guidelines.

I have arrived at heat load considering
1 wall transimission load
2 Air change ( Infilteration) load
3 product load ( sensible,latent,respiration)
4 electrical and occupancy load.

But for given load how to arrive to surface area ( Primary and secondary) and air flow desired which will keep RH 90% and desired temp between +5 to +10 degree celcius.

I will be grateful for your help

Thanks Sunil Bhat

Hi there,

You must either know the air cooler design or use the evaporator manufacturer's catalogs.
Cold room evaporator is selected by :
evaporating temperature, capacity, temperature difference

For high RH you have to select an evaporator with low TD, like 5°C.

Cheers

[paul_h]

Big coils with low TD's is what you want. The lower the TD the higher the room RH. If you really want to get it spot on use a psych chart and plot you desired conditions.

Exactly, high surface area and low TD to minimise moisture removal from the air, but a large enough coil to handle the load with a small TD.
Maybe it would help if you said what the total load is and what refrigerant for each room. Edit: and what condensing units you are using

[Samarjit Sen]

Dear Sunil Bhat,

For knowing the details of the Evaporator, you will have to depend on the manufacturers catalogs or use the Evaporator Coil Selection software of Helpman Roller or Guntner. It will give you the correct figures. Do not try to work this out yourself, as doing the same is very difficult.

In case you want some more assistance, please do contact me. I presume your requirement is for Fruit Precooling and Storage.